Purely osteolytic bone lesions in the early osteoarticular phase of synovitis, acne, pustulosis, hyperostosis and osteitis syndrome.

SAPHO syndrome (synovitis, acne, pustulosis, hyperostosis and osteitis) is a rare chronic inflammatory disorder characterised by sterile osteitis, typically associated with osteosclerotic changes and neutrophilic cutaneous manifestations. In the early osteoarticular phase, before osteosclerotic changes become apparent, bone lesions may appear purely osteolytic, complicating diagnosis. We report a woman in late adolescence who presented with anterior chest and low back pain. CT demonstrated purely osteolytic lesions in the manubrium and first lumbar vertebra, raising suspicion of malignancy or infectious osteomyelitis. Careful history-taking and cutaneous examination revealed palmoplantar pustulosis, leading to a working clinical diagnosis of SAPHO syndrome, although a bone biopsy was not performed due to the patient's preference. This case highlights a diagnostic pitfall of SAPHO syndrome in its early osteoarticular phase and underscores the importance of meticulous cutaneous assessment when evaluating unexplained osteolytic bone lesions.